A gas turbine power plant generally includes a compressor that compresses combustion air, a combustor that mixes the compressed combustion air with gas turbine fuel (hereinafter referred to as fuel) to thereby burn a fuel-air mixture and generate combustion gas at high temperature, and a turbine that uses the combustion gas to drive the compressor and a generator.
A pre-mixed combustion system that mixes air with fuel in advance of combustion is employed as a fuel control system for such a gas turbine power plant in order to reduce nitrogen oxide emissions produced in the combustor. In the pre-mixed combustion system, the combustor is configured to include a plurality of burners and fuel systems. By using these burners and fuel systems, a pre-mixed combustion portion of the combustor is divided into a plurality of sub-portions to thereby increase or decrease the number of active combustion portions according to operating load. Specifically, a known method (combustion switching) uses one fuel system at starting to allow part of the burners to burn fuel; as a fuel flow rate thereafter increases, the number of fuel systems used is increased and the burners yet to be ignited are ignited in sequence, thereby increasing the number of active combustion portions (see, for example, Patent Document 1).
Another known arrangement includes a water atomization cooling apparatus disposed at an inlet to a compressor. The water atomization cooling apparatus sprays water drops over the combustion air in order to improve an output and efficiency of the gas turbine power plant (see, for example, Patent Document 2). Spraying water drops over the combustion air improves the output thanks to a reduced air temperature and an increased air flow rate on one hand; but, on the other hand, a reduced fuel-air ratio results immediately after the start of water drop spraying, which increases a risk of misfire in the combustor. The water atomization cooling apparatus is therefore started after the gas turbine power plant enters a rated operation mode (see, for example, Patent Documents 3 and 4).